Deeper insight into Gambierdiscus polynesiensis toxin production relies on specific optimization of high-performance liquid chromatography-high resolution mass spectrometry

Sulfo-Gambierones, Two New Analogs of Gambierone Produced by Gambierdiscus excentricus

“…The proposed fragmentation pathway concerning the cluster from m/z 627.3852 (−6.2 ppm) to m/z 591.3635 (−7.6 ppm) was the opening of C-and D-cycles. This type of fragmentation is commonly observed for other polyethers [20], but was not found in either gambierone or sulfo-gambierone. The small fragments reported from m/z 289.1799 (−0.3 ppm) to m/z 121.0649 (+0.8 ppm) corresponded to the ones found in sulfo-gambierone based on our hypothesis (i.e., the double bond conjugated system that induces either a carbonyl or a hydroxyl for the right-hand side of the molecule).…”

“…In positive ionization mode (ESI + ), the chromatographic peak at 6.7 min did not present any ions with a mass related to the expected [M+H] + at m/z 1039.4931 (Figure S2C) but the ion m/z 1056.5047 could correspond to the ammonium adduct [M+NH 4 ] + of 44-methylgambierone, however, with a mass error of −14.1 ppm. In addition, the protonated molecule, sodium adducts and several in-source water losses commonly observed for gambierones, ciguatoxins or related cyclic polyethers [20,45] were not observed for this compound, which also suggests a weak structural resemblance with 44-methylgambierone.…”

“…In order to reduce in-source fragmentation and to obtain a higher intensity for the [M+H] + of the sulfated gambierone analog, a new method adapted from Yon et al [20] was implemented; method 3 (See Section 3.8). The resulting full scan in ESI + mode presented in Figure 2C revealed a much greater abundance of sulfated ion (i.e., from m/z 1105.4342 to 1069.4131) and its corresponding ammonium and di-ammonium adducts (m/z 1122.4608 and 1139.4874, respectively) with high mass accuracy (Table 2).…”

“…Method 2 was adapted from Sibat et al [43] (able to detect a wide range of compounds): ESI positive and negative, gas temperature 160 • C, gas flow 11 L min −1 , nebulizer 45 psi, sheath gas temperature 150 • C and sheath gas flow 11 L min −1 , capillary voltage at +/−4500 V, nozzle voltage at 500 V, fragmentor at 365 V and ion funnel low pressure, high pressure and exit at 200 V, 100 V and 50 V, respectively. Method 3 (optimized for gambierone and adapted from Yon et al [20]): ESI positive only, gas temperature 150 • C, nebulizer 35 psi, sheath gas temperature 250 • C and sheath gas flow 6 L min −1 , capillary voltage at +3500 V, nozzle voltage at 1000 V, fragmentor voltage at 135 V and ion funnel low pressure, high pressure and exit at 200 V, 200 V and 50 V, respectively.…”

“…To date, only the species G. polynesiensis (previously identified as G. toxicus [8]) was demonstrated by analog-specific methods, such as liquid chromatography coupled to tandem or high-resolution mass spectrometry (LC-MS/MS or LC-HRMS), as a ciguatoxin producer in the Pacific Ocean [19] with more than 14 ciguatoxin analogs identified [20]. The biotransformation of ciguatoxins produced by this species as they passed through the food chain from dinoflagellates to fish has been elucidated [21][22][23].…”